Fix mbl_mesh_report

Marlin/Marlin_main.cpp

     SERIAL_PROTOCOLPGM("Z offset: "); SERIAL_PROTOCOL_F(mbl.z_offset, 5);
     SERIAL_PROTOCOLLNPGM("\nMeasured points:");
     print_2d_array(GRID_MAX_POINTS_X, GRID_MAX_POINTS_Y, 5,
-      [](const uint8_t ix, const uint8_t iy) { return mbl.z_values[ix][iy]; }
+      [](const uint8_t ix, const uint8_t iy) { return mbl.z_values[iy][ix]; }
     );
   }